The present invention relates in general to power saws, and more particularly to a power chain saw unit for cutting notches in roof rafters.
In the framing of buildings, notches are formed in the lower end portion of each roof rafter for accommodating the rafter plate. Heretofore, notches in roof rafters were cut individually by hand saws or by electrical circular saws. Subsequently, power saws were employed to cut notches in a series of side-by-side roof rafters. The conventional electrical circular saw was not able to cut at an angle exceeding 45.degree. to meet the seat cut angle requirement. In the past, the seat cut in the notches of roof rafters was difficult to make when cutting notches in a series of roof rafters. Also, as the cutting angle of the electrical circular saw blade was increased in cutting notches in a series of roof rafters, the depth of the seat cut was reduced.
In the cutting of notches in a series of roof rafters, it was heretofore the practice to use a large circular saw with a table. This arrangement was still limited in cutting the depth of the seat cut. Another arrangement heretofore used for the cutting of notches in a series of roof rafters was to use a large circular saw with a series of blades integral with the arbor shaft of the circular saw. The blades rotated and chipped out the seat cut. This arrangement had relatively large torque requirements and a heavy load was imposed on the motor to rotate the blades through solid wood mass.
The Allemann, U.S. Pat. No. 2,925,104, issued on Feb. 16, 1960, for Combination Chain-And-Circular-Saw Portable Power Saw Unit discloses a portable power saw for cutting notches in roof rafters. The portable power saw includes the combination of a circular saw blade and a chain saw blade to cut the notch in the roof rafter.
In the Vizziello et al., U.S. Pat. No. 3,799,224, issued on Mar. 26, 1974, for Rafter Beam Nothing Apparatus, there is disclosed a power driven rotary saw mounted on a pair of rods, which travel horizontally in unison through the superstructure of a frame. The frame includes a table for horizontal placement thereon of a rafter beam to be notched.
In the Burch, U.S. Pat. No. 3,078,885, issued on Feb. 26, 1963, for Portable Power Hand-Guided Saw Mounting Drive, there is disclosed an adapter for a power saw having a disc blade. The disc blade cuts a slit in plywood panels at a predetermined angle relative to the surface of the plywood panel.
The Marsan, U.S. Pat. No. 4,290,464, issued on Sept. 22, 1981, for a Holder For Portable Electric Cutting Instrument, discloses a holder comprising a base plate having a planar bottom surface. An aperture is formed in the base plate through which a cutting tool projects. A rigid harness interconnects angular adjustment means with clamping means for the cutting instrument to provide tilting of the cutting instrument at an angle at least 45.degree..
The Edmunson, U.S. Pat. No. 3,845,556, issued on Nov. 5, 1974, for Cut Control Attachment For Chain Saws, discloses a sole plate with slots for attachment to a chain saw guide bar. An angle-adjustable guide bar yoke bracket is adjustably carried by the sole plate for adjusting the cutting angle of the chain saw.
In the Granberg et al., U.S. Pat. No. 4,070,757, issued on Jan. 31, 1978, for Log Sawing Attachment For A Chain Saw, there is disclosed a movable guide frame which can be clamped to the cutter bar of the chain saw. The frame guides the chain saw to make cuts of a pre-selected depth.
In the Slonaker, U.S. Pat. No. 1,170,120, issued on Feb. 1, 1916, for Portable Chain Mortising Machine, there is disclosed a device having a plate secured to wood to be bored. The plate is held from displacement by tines.